This firepit was built with concrete landscape pavers, but the idea looked so interesting and practical that I decided to post it here as an example of what could be done with geopolymer. You could make blocks for your firepit or even start a small business.

Sodium hydroxide (NaOH), also known as lye and caustic soda, is a caustic metallic base. It is used in many industries, mostly as a strong chemical base in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents and as a drain cleaner.

Pure sodium hydroxide is a white solid available in pellets, flakes, granules, and as a 50% saturated solution. It is hygroscopic and readily absorbs water from the air, so it should be stored in an airtight container. It is very soluble in water with liberation of heat.

Of historic interest is the Leblanc process, which produced sodium carbonate, followed by roasting to create carbon dioxide and sodium oxide, which readily absorbs water to create sodium hydroxide. This method is still occasionally used. It helped establish sodium hydroxide as an important commodity chemical. The Leblanc process was superseded by the Solvay process in the late 19th century.

Sodium hydroxide is the principal strong base used in the chemical industry. In bulk it is most often handled as an aqueous solution, since solutions are cheaper and easier to handle. Sodium hydroxide, a strong base, is responsible for most of these applications. Another strong base such as potassium hydroxide is likely to yield positive results as well.

56% of sodium hydroxide produced is used by the chemical industry, with 25% of the same total used by the paper industry.

Sodium hydroxide is used in the home as a drain cleaning agent for clearing clogged drains. It is distributed as a dry crystal or as a thick liquid gel.

Safety warning:
Solid sodium hydroxide or solutions of sodium hydroxide may cause chemical burns, permanent injury or scarring if it contacts unprotected human, or other animal, tissue. It may cause blindness if it contacts the eye. Protective equipment such as rubber gloves, safety clothing and eye protection should always be used when handling the material or its solutions.

Dissolution of sodium hydroxide is highly exothermic, and the resulting heat may cause heat burns or ignite flammables. It also produces heat when reacted with acids. Sodium hydroxide is corrosive to some metals, e.g. aluminum, which produces flammable hydrogen gas on contact. Sodium hydroxide is also mildly corrosive to glass, which can cause damage to glazing or freezing of ground glass joints.

SYDNEY: A by-product from coal-fired power stations can be made into a stronger and much safer concrete with far less carbon dioxide emissions, researchers have found. They say this technology could “revolutionise the world’s building and construction industries” and they hope to move the technology towards a large-scale trial and commercialisation. Materials scientist William Rickard and his colleagues from Curtin University, in Perth, used waste materials called ‘fly ash’ to create the concrete.

Fireproof concrete may save lives
“The main benefit of using fly ash polymer cements is that they maintain their strength up to 1,200ºC whereas traditional cements start losing their strengths at about 600ºC … In the event of a fire, a building using traditional cement can lose its strength and collapse.
Buildings with fly ash concrete would have a much better chance of surviving a fire, Rickard says. Even coating exposed structural steel with it would reduce the heat that goes through the steel and prevent combustion. Each year there are approximately 100 fatalities and about 3,000 injuries from structural fires in Australia alone.

As well recycling, the fly ash cement will be good for the environment because it releases up to 80% less carbon dioxide than standard cement.
It could make a big different on a global scale. “[Currently] 5–8% of the world’s carbon emissions come from the manufacture of traditional cement,” says Rickard.

Snippets from their report:
– No visible defects or deformation could be observed after 150 [freezing] cycles.
– It is obvious from the results obtained that the geopolymers materials on the basis of the fly ash possess an excellent frost resistance.
– Geopolymer mortars and concretes kept in the NaCl solution for long periods of time resist to corrosion without showing any signs of sample damage.
– The resistance of geopolymer concretes to the action of salt solutions is better than that of [Portland] cement-based concrete.
– The geopolymers’ strength is affected substantially by macro-pores (103 nm and more) formed in result of the air entrained into the geopolymers; these may also be fly ash particles that underwent only partial reaction.
– No shrinkage due to hydration (typical for the cement-based concretes) takes place in the concrete. The strength values of the geopolymer concrete increase in the long run.
– The geopolymer concrete is resistant to the corrosive environments.

Basalt is a natural material that is found in volcanic rocks. It is mainly used (as crushed rock) in construction, industrial and high way engineering. One can also melt basalt (1300-1700°C) and spin it into fine fibres. When used as (continuous) fibres, basalt can reinforce a new range of (plastic and concrete matrix) composites.

The purpose of this work was to investigate the influence of the volumetric fraction of the fibers on the fracture toughness of geopolymeric cement concretes reinforced with basalt fibers. The values of fracture toughness, critical stress intensity factor and critical crack mouth opening displacement were measured on 18 notched beams tested by three-point bending. The a0=h (notch height/beam height) ratio was equal to 0.2 and the L0=h (distance between the supports/beam height) ratio was equal to 3. According to the experimental results, geopolymeric concretes have better fracture properties than conventional Portland cement. They are also less sensitive to the presence of cracks.

5,000 lb. geopolymer block: Researchers at Tech developing a new type of concrete from 'fly ash'

Where many coal-fired power plants see waste, researchers at Louisiana Tech University see an opportunity to curb greenhouse gas emissions, protect aquifers and change engineering forever.

The researchers, led by Erez Allouche, an assistant professor of civil engineering and associate director of the Trenchless Technology Center, and Sven Eklund, an assistant professor of chemistry, are working with a group of students to create a geopolymer concrete, or GPC, made from a waste byproduct produced by coal-fired power plants called “fly ash.”

The researchers use another byproduct from the paper pulp industry, sodium hydroxide, to start the reaction that turns fly ash into GPC.

So far, the Tech research team has produced a 5,000 pound block of GPC and constructed a 100-square foot gazebo made entirely of GPC.

Allouche said he foresees GPC being used for road and bridge construction, as well as for other civil-engineering products like sewer piping.

The researchers could reach that goal sooner rather than later, as Allouche said they are currently on the verge of marketing a sprayable geopolymer product.

GPC currently costs about 15 percent more than Portland cement, “but that does not take into account savings (produced) by not having to store fly ash or ‘green’ tax credits,” Allouche said.